Gilbert Quevauvilliers notes an implication:
Yes, you read that right, it is possible where you have shared Power BI semantic model with an external (guest user in Entra ID) they can now connect to the semantic model using Excel.
This has been around for quite a while I just did not know about it, here is the Microsoft documentation: Semantic model connectivity and management with the XMLA endpoint in Power BI – Power BI | Microsoft Learn
The first thing to note is that this currently only works in the Excel Desktop App.
I did try using Excel on the Web and unfortunately that did not work.
I then created my Excel file, uploaded to SharePoint Online and tried to interact with the Excel Pivot table and that too did not work.
Ok enough of the limitations let me show you how to get it working.
Click through to see how. Gilbert also has an important note about row-level security, co read the whole thing.